An ambient temperature molten salt is a generic name for salts which exist in a liquid state around ambient temperature (ambient temperature), and imidazolium-based, pyridium-based, alicyclic amine-based, aliphatic amine-based and aliphatic phosphonium-based are known as kinds of a cationic segment. Further, it is known that, because of its excellent nonvolatility and voltage endurance, an ambient temperature molten salt is used as an electrolyte of an electrochemical device. For example, in Patent Literature 1, a secondary battery provided with positive and negative electrodes, at least one electrode of which is a conductive polymer, and a liquid electrolyte composed of an ambient temperature molten salt is disclosed.
Further, in Patent Literature 2, there is disclosed an all-solid lithium secondary battery, in which an ionic liquid (an ambient temperature molten salt) having 1-ethyl-3-methylimidazolium as a cationic segment exists in a pinhole of a solid electrolyte layer. This technique is intended for preventing an internal short circuit of the battery by having the ionic liquid exist in a pinhole of the solid electrolyte layer.
On the other hand, it is known that an ambient temperature molten salt is used as an agent for preventing a charge-up, which prevents an electric charge from building up in a measuring object during measurement by an electron microscope. For example, in Patent Literature 3, an agent for preventing a charge-up for an electron microscope with the use of an ionic liquid (an ambient temperature molten salt) is disclosed. ‘Charge-up’ generally signifies a phenomenon such that an appropriate result is not obtained for the reason that a measuring object (such as an insulator) becomes charged during measurement with the use of electron rays or the like. For example, in measurement with the use of a scanning electron microscope (SEM), in the case where a secondary electron emission amount is more than a primary electron incidence amount, occasionally, a measuring object becomes positively charged during the measurement and an obtained display of a whole SEM image may become white in some occasion.